The present invention relates to laterally substituted curable Liquid Crystals (LCPs) having mesogenic properties or properties which cause these LCPs to be compatible with a mesogenic molecular structure. In particular the present invention relates to laterally substituted curable Liquid Crystals (LCPs) with adjustable optical anisotropy and in parallel with low melting point or good supercoolability, relatively high clearing point and good alignment properties and the use of such LCPs in the preparation of substantially uniform or patterned film in which the orientation of the LCP molecules in the plane and relative to the plane of the substrate can be controlled.
Films prepared from curable Liquid Crystals (LCP films) are well known to a skilled person and are used in the preparation of optical and electro-optical devices. U.S. Pat. No. 5,650,534 discloses compounds and mixtures used to prepare components suitable for use non-linear optical (NLO) applications. These compounds are optically active and exhibit chiral smectic or chiral nematic mesophases. U.S. Pat. No. 5,707,544 also discloses compounds and mixtures suitable for use in NLO applications. However, these compounds are characterised by relatively high melting points. U.S. Pat. No. 5,593,617 discloses photochemically polymerisable liquid crystal compounds and mixtures, which are used to prepare optical and electronic components. However, these mixtures have a relatively narrow operating range and are unsuitable for use at higher temperatures.
LCP films are generally manufactured by using known coating techniques such as spin coating. This involves casting an organic solution of a cross-linkable LCP or LCP mixture onto a substrate provided with an orientation layer. The organic solvent is subsequently removed to give a well-oriented, solvent-free mesogenic LCP layer, which in turn is cross-linked to give an LCP film. The desired optical performance of such films depends crucially on some reproducible physical parameters which the LCP material has to fulfill simultaneously. Such properties are a nematic mesophase, a high clearing point, a low melting point or a low tendency to crystallise when cooled below melting point (supercooling), good solubility in organic solvents, good miscibility with other LCPs, good aligning properties on orientation layers, and the ability to form an adjustable tilt out of the substrate plane essentially free of tilt domains and disclinations. Tilt domains are regions within the LCP film in which the long axes of the LCP molecules form tilt angles out of the plane of the substrate of the same size but in opposite direction. Disclinations are borderlines of neighbouring tilt domains where LCP molecules of opposite tilt angles are adjacent. These tilt domains and disclinations result in both a disturbance in the uniform appearance of the film and an inhomogeneous optical performance.
Good aligning properties and the ability to form an adjustable tilt angle are of particular relevance if photo-orientated and photo-patterned orientation layers are used for the orientation of LCPs. This so-called linear photo-polymerisation (LPP) technology (cf. e.g. Nature, 381, p. 212 (1996)) allows the production of not only uniform but also structured (photo-patterned) orientation layers. If such structured orientation layers are used for the orientation of LCPs, the LCP molecules should adapt the information given by the orientation layer with respect to the direction of alignment and the tilt angle.
For adjusting the optical properties of the layers and films prepared from LCPs as for example retardation films, it is further essential to have available a variety of LCP materials with differing optical anisotropy, mainly high optical anisotropy. It is known that LCPs exhibiting a high optical anisotropy often show a negative impact on several of the above properties. Particularly the formation of smectic mesophases, high melting points, an enhanced tendency to crystallise, a low solubility in organic solvents or reduced miscibility with other LCPs is observed. Furthermore the ability of homogeneous alignment free of tilt domains and disclinations is often reduced.
There is, therefore, a need for a new LCP material that may be used in the preparation of an LCP mixture, which significantly reduces the aforementioned disadvantages. The present invention addresses that need.
A first aspect of the invention provides a compound of formula (I) 
wherein
G1 and G2 independently represent a polymerisable mesogenic residue;
X represents a group selected from xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CONRxe2x80x2xe2x80x94, xe2x80x94OCOOxe2x80x94, xe2x80x94OCONRxe2x80x2;
Sp represents a group of the formula xe2x80x94(CH2)pxe2x80x94 in which p is an integer of 1 to 18 and in which one or two non adjacent xe2x80x94CH2xe2x80x94 groups are optionally replaced by xe2x80x94CHxe2x95x90CHxe2x80x94; or in which one or two xe2x80x94CH2xe2x80x94 groups are optionally replaced by one or two groups selected from the group consisting of xe2x80x94Oxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CONRxe2x80x2xe2x80x94, xe2x80x94OCOOxe2x80x94, xe2x80x94OCONRxe2x80x2 with the proviso that firstly the spacer group does not contain two adjacent heteroatoms and secondly when X is xe2x80x94CH2xe2x80x94, p can also have a value of 0; and
M represents an achiral group of formula (II) 
xe2x80x83in which
A and B independently represent a six membered isocyclic or heterocyclic group or naphthalenediyl;
C is selected from the group consisting of a five and six membered isocyclic or heterocyclic group or naphthalenediyl;
n1 and n2 are 0 or 1 with the proviso that firstly 1xe2x89xa6n1+n2xe2x89xa62 and secondly, when C is naphthalenediyl 0xe2x89xa6n1+n2xe2x89xa62;
Z1 is selected from the group consisting of xe2x80x94Oxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CONRxe2x80x2xe2x80x94, xe2x80x94NRxe2x80x2COxe2x80x94, OCOOxe2x80x94, xe2x80x94OCONRxe2x80x2xe2x80x94, xe2x80x94NRxe2x80x2COOxe2x80x94 and a single bond;
xe2x80x83in which
Rxe2x80x2 is selected from the group consisting of hydrogen, a lower achiral alkyl group and a lower achiral alkenyl group;
Z2 and Z3 are independently selected from the group consisting of single bond, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94(CH2)4xe2x80x94 and xe2x80x94(CH2)3Oxe2x80x94; and
R1 is selected from the group consisting of xe2x80x94CN, xe2x80x94COR, xe2x80x94COOR, xe2x80x94OCOR, xe2x80x94CONRxe2x80x2R, xe2x80x94NRxe2x80x2COR, OCOOR, xe2x80x94OCONRxe2x80x2R, xe2x80x94NRxe2x80x2COOR, xe2x80x94F, xe2x80x94Cl, xe2x80x94CF3, xe2x80x94OCF3, xe2x80x94OR and xe2x80x94R
xe2x80x83in which
R is selected from the group consisting of hydrogen, an achiral C1-18 alkyl group and an achiral C4-18 is alkenyl group with the double bond at 3-position or higher; and
Rxe2x80x2 is as defined above;
with the proviso that at most one of the rings A, B and C is a naphthalenediyl group.
In addition to the laterally substituted mesogenic compounds referred to above, such compounds are also disclosed in WO 95/24454 and WO 95/24455. However, many of these compounds are not suitable for preparing LCP films with high optical anisotropy without one or more of the aforementioned disadvantages. It has been found that by using the compounds of the present invention it is possible to control the optical anisotropy of LCPs without significant increase of melting point or decrease of clearing point. In addition they generally have a surprisingly low tendency to crystallise even far below the melting point (good supercoolability). Furthermore they generally exhibit enhanced alignment properties especially on structured LPP orientation layers, they are able to form tilt angles and show a decreased tendency to form tilt domains and disclinations. Furthermore the compounds of the invention have a comparatively good solubility in organic solvents and a high miscibility with other LCP compounds.
The optical anisotropy of the compounds of the invention may be easily adapted to requirements only by selecting different groups of M of formula I without changing the main core of the molecule. This allows an economical access to a broad range of LCPs exhibiting different optical anisotropies with a minimum of chemical steps in their production.
The polymerisable mesogenic residues G1 and G2 may be the same or different, but are preferably the same.
The group X is preferably selected from the group consisting of xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COOxe2x80x94 and xe2x80x94OOCxe2x80x94.
The spacer group Sp may be optionally substituted by one or more fluorine or chlorine atoms. Groups in which there are no substituent groups present are preferred. It is especially preferred that the integer p has a value of from 1to 12 and that no more than two xe2x80x94CH2xe2x80x94 groups are replaced by xe2x80x94Oxe2x80x94 and that no more than one xe2x80x94CH2xe2x80x94 group is replaced by one group selected from the group consisting of xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CONRxe2x80x2xe2x80x94, xe2x80x94OCOOxe2x80x94 and xe2x80x94OCONRxe2x80x2.
The groups A and B comprising the achiral group M are either saturated, unsaturated or aromatic. They are optionally substituted by one or two substituents selected from the group consisting of F, Cl, CN, a lower alkyl, lower alkenyl, lower alkoxy and lower alkenyloxy. Preferably the groups A and B each contain no more that one substituent. It is especially preferred that the groups A and B contain no substitution.
It is preferred that the groups A and B are selected from the group consisting of 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl, 1,4-naphthalenediyl and 2,6-naphthalenediyl. Is it especially preferred that A and B are selected from the group consisting of 1,4-phenylene, trans-1,4-cyclohexylene and 2,6-naphthalenediyl.
The group C comprising the achiral group M is either saturated, unsaturated or aromatic. It is optionally substituted with one or two substituents selected from the group consisting of F, Cl, CN, a lower alkyl, lower alkenyl, lower alkoxy and lower alkenyloxy. It is preferred that the group C contains at most one substituent. It is especially preferred that the group C contains no substitution.
It is preferred that the group C is selected from furan-2,4-diyl, furan-2,5-diyl, tetrahydrofuran-2,4-diyl, tetrahydrofuran-2,5-diyl, dioxolane-2,4-diyl, dioxolane-2,5-diyl, oxazole-2,4-diyl, oxazole-2,5-diyl, cyclopentane-1,3-diyl, cyclopentane-1,4-diyl, 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, trans-1,4-cyclohexylene or dioxane-2,5-diyl, 1,4-naphthalenediyl and 2,6-naphthalenediyl. It is especially preferred that C is selected from the group consisting of furan-2,5-diyl, tetrahydrofuran-2,5-diyl, oxazole-2,5-diyl, 1,4-phenylene, trans-1,4-cyclohexylene, and 2,6-naphthalenediyl.
The group Z1 comprising the achiral group M is preferably selected from the group consisting of xe2x80x94Oxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94 and a single bond. It is especially preferred that Z1 is selected from xe2x80x94Oxe2x80x94 or a single bond.
The groups Z2 and Z3 comprising the achiral group M are preferably selected from the group consisting of xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94 and a single bond. It is especially preferred that Z2 and Z3 are selected from the group consisting of xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94 and a single bond.
The group R1 comprising the achiral group M is preferably selected from the group consisting of xe2x80x94CN, xe2x80x94COOR, xe2x80x94OCOR, F, Cl, CF3, OCF3, OR, R, in which R represents a C1-12 achiral alkyl, C4-12 achiral alkenyl group with the double bond at position 3- or higher, or hydrogen. It is especially preferred that R1 is selected from the group consisting of xe2x80x94CN, F, Cl, CF3, OCF3, OR, R, in which R represents a C1-8 achiral alkyl group or hydrogen.
By the term xe2x80x9clower alkylxe2x80x9d it should be understood to include a C1-6 achiral, branched or straight-chained alkyl group. Examples of lower alkyl groups that may be present in the compounds of the invention include methyl, ethyl, propyl, butyl, pentyl hexyl and the like.
By the term xe2x80x9clower alkenylxe2x80x9d it should be understood to include C3-6 achiral, branched or straight-chained alkenyl group in which the double bond is at position 2- or higher. Examples of lower alkenyl groups that may be present in the compounds of the invention include 2-propenyl, 3-butenyl, 3-isopentenyl, 4-pentenyl, 5-hexenyl, 4-isohexenyl and the like.
By the term xe2x80x9clower alkoxyxe2x80x9d it should be understood to include C1-6; achiral, branched or straight-chained alkoxy group. Examples of lower alkoxy groups that may be present in the compounds of the invention include methoxy, ethoxy, propoxy, butoxy, pentoxy hexoxy and the like.
By the term xe2x80x9calkenyloxyxe2x80x9d it should be understood to include C3-6 achiral, branched or straight-chained alkenyloxy group in which the double bond is at position 2- or higher. Examples of lower alkenyloxy groups that may be present in the compounds of the invention include 2-propenyloxy, 3-butenyloxy, 4-pentenyloxy, 5-hexenyloxy and the like.
Preferably the polymerisable mesogenic residues G1 and G2 are each independently represented by the group of formula III 
wherein
D and E are independently selected from the group consisting of 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, trans-1,4-cyclohexylene and trans-1,3-dioxane-2,5-diyl;
m is 1 or 0,
Z4 and Z5 are independently selected from the group consisting of a single bond, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94(CH2)4xe2x80x94 and xe2x80x94(CH2)3Oxe2x80x94;
Z6 represent a group of formula xe2x80x94(CH2)pXxe2x80x94 in which p is an integer having a value of 1 to 18 and X is defined above, and in which one or two non adjacent xe2x80x94CH2xe2x80x94 groups may be optionally replaced by xe2x80x94CHxe2x95x90CHxe2x80x94 or in which one or two xe2x80x94CH2xe2x80x94 groups may be replaced by one or two additional linking groups X with the proviso that firstly the group Z6 does not contain two adjacent heteroatoms and secondly when X is xe2x80x94CH2, p can also have a value of 0
R2 represents a polymerisable group selected from the group consisting of CH2xe2x95x90C(Ph)xe2x80x94, CH2xe2x95x90CWxe2x80x94COOxe2x80x94, CH2xe2x95x90CHxe2x80x94COOxe2x80x94Phxe2x80x94, CH2xe2x95x90CWxe2x80x94COxe2x80x94NHxe2x80x94, CH2xe2x95x90CHxe2x80x94Oxe2x80x94, CH2xe2x95x90CHxe2x80x94OOCxe2x80x94, Phxe2x80x94CHxe2x95x90CHxe2x80x94, CH2xe2x95x90CHxe2x80x94Phxe2x80x94, CH2xe2x95x90CHxe2x80x94Phxe2x80x94Oxe2x80x94, R3xe2x80x94Phxe2x80x94CHxe2x95x90CHxe2x80x94COOxe2x80x94, R3xe2x80x94OOCxe2x80x94CHxe2x95x90CHxe2x80x94Phxe2x80x94Oxe2x80x94 and 2-W-epoxyethyl
xe2x80x83in which
W represents H, Cl, Ph or a lower alkyl,
R3 represents a lower alkyl with the proviso that when R3 is attached to a phenylene group (xe2x80x94Phxe2x80x94) it may also represent hydrogen or a lower alkoxy.
The terms xe2x80x9cPhxe2x80x9d and xe2x80x9cPhxe2x80x94xe2x80x9d will be understood to indicate a phenyl group. The term xe2x80x9cxe2x80x94Phxe2x80x94xe2x80x9d will be understood to mean any isomer of phenylene, namely 1,2-phenylene, 1,3-phenlylene or 1,4-phenylene, except where the context requires otherwise.
The groups D and E are optionally substituted with one or two halogens, xe2x80x94CN, lower alkyl, lower alkenyl, lower alkoxy or lower alkenyloxy groups. If halogen substituents are present they are preferably F or Cl. It is preferred that the groups D and E are selected from optionally substituted 1,4-phenylene and 1,4-cyclohexylene rings. It is especially preferred that the groups D and E contain no substitution.
It is preferred that the groups Z4 and Z5 are selected from the group consisting of a single bond, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94CH2xe2x80x94CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 and xe2x80x94Cxe2x89xa1Cxe2x80x94. It is especially preferred that Z4 and Z5 represent a single bond, xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94COOxe2x80x94or xe2x80x94OOCxe2x80x94.
Z6 may be optionally substituted by one or more halogen atoms, preferably one or more fluorine atoms. It is preferred that p has a value of 1 to 11. It is also preferred that Z6 contains no substitution. It is further preferred that, for the group Z6, X is selected from xe2x80x94CH2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94COOxe2x80x94 and xe2x80x94OOCxe2x80x94, especially xe2x80x94CH2xe2x80x94 or xe2x80x94Oxe2x80x94.
It is preferred that the group R2 is selected from the group consisting of CH2xe2x95x90CWxe2x80x94COOxe2x80x94 and CH2xe2x95x90CHxe2x80x94Oxe2x80x94.
It is preferred that the sum of the two integers m for each of the groups G1 and G2 is 0 or 1. It is especially preferred that for both G1 and G2 m has a value of 0.
The compounds of the invention may be readily prepared using procedures well known to a skilled person in accordance with any one of the procedures set out in Schemes 1 and 2 below. 
in which:
DEAD is diethyl azodicarboxylate
TPP is triphenylphospine
THF is tetrahydrofuran
KI is potassium iodide
DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene
EDC is N-(3-dimethylaminopropyl)-Nxe2x80x2-ethylcarbodiimide hydrochloride
DMAP is 4-dimethylaminopyridine
Suitable starting materials used in the preparation of the compounds of the present invention include, amongst others, phenyl and biphenyl alcohol and carboxylic acid compounds as well as 1,4-cyclohexanedione. The starting materials are commercially available or may be readily prepared and are well known to a skilled person.
The compounds of the invention are preferably prepared by forming a ring that includes a lateral group prior to linking the mesogenic residues. Alternatively, the compounds may be prepared by forming a ring that includes a polymerisable mesogenic residue prior to linking the lateral group. A second aspect of the invention therefore provides a method of preparation of a compound of formula (I), the method comprising forming a ring that includes a lateral group and subsequently linking the mesogenic residue thereto. The mesogenic residues G1 and G2 are preferably connected to the central ring simultaneously. As indicated above, it is especially preferred that the mesogenic residues G1 and G2 are identical.
It will be appreciated that the compounds of the invention may be used in the preparation of liquid crystalline mixtures. Such mixtures may be prepared by admixing a compound of formula (I) with one or more additional components. An organic solvent may also be used in the preparation of these mixtures. A third aspect of the invention therefore provides a liquid crystalline mixture comprising a compound of formula (I) and one or more additional components. The one or more additional components present in the liquid crystalline mixture may be further compounds of formula (I), other mesogenic compounds, compounds that are compatible with a mesogenic molecular architecture or chiral dopants for the induction of helical pitch. The LCP mixture may also include a suitable organic solvent. Examples of solvents that may be used in the preparation of such liquid crystalline mixtures include anisole, N-methylmorpholine, caprolactone, cyclohexanone, methyl ethyl ketone and the like.
Examples of additional components that may be used in the preparation of liquid crystalline LCP mixtures according to the third aspect of the invention include those compounds represented by formulae III to X. 
in which
R4 is selected from the group consisting of CH2xe2x95x90CHxe2x80x94Oxe2x80x94, CH2xe2x95x90CHxe2x80x94COOxe2x80x94, CH2xe2x95x90C(CH3)xe2x80x94COOxe2x80x94, CH2xe2x95x90C(Cl)xe2x80x94COOxe2x80x94 and 
S3, S4 independently represent xe2x80x94(CH2)nxe2x80x94 or xe2x80x94O(CH2)nxe2x80x94;
E1, E2 are independently selected from the group consisting of 1,4-phenylene trans-1,4-cyclohexylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl and trans 1,4-cyclohexylene-1,4-phenylene;
F1, F2 are independently selected from the group consisting of 1,4-phenylene, and 2- or 3-fluoro-1,4-phenylene;
L4, L5, L6 are independently selected from the group consisting of OH, C1-C20-alkyl, C1-C20-alkenyl, C1-C20-alkoxy, C1-C20-alkoxy-carbonyl, formyl, C1-C20-alkylcarbonyl, C1-C20-alkylcarbonyloxy, halogen, cyano and nitro;
Z7 is selected from the group consisting of xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94O(CH2)3xe2x80x94, xe2x80x94OOC(CH2)2xe2x80x94 and xe2x80x94COO(CH2)3xe2x80x94;
Z8 is selected from the group consisting of a single bond, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, xe2x80x94(CH2)4xe2x80x94, xe2x80x94O(CH2)3xe2x80x94, (CH2)3Oxe2x80x94 and xe2x80x94Cxe2x89xa1Cxe2x80x94;
Z9 is selected from the group consisting of a single bond, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94, xe2x80x94OCH2xe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94OOCxe2x80x94, and xe2x80x94Cxe2x89xa1Cxe2x80x94;
Y is independently selected from the group consisting of hydroxy, C1-C20-alkyl, C1-C20-alkenyl, C1-C20-alkoxy, C1-C20-alkoxycarbonyl, formyl-, C1-C20-alkylcarbonyl, C1-C20-alkylcarbonyloxy, fluoro, chloro, bromo, cyano and nitro;
n is an integer having a value of from 2 to 20; and
v is an integer having a value of from 2 to 12
The compounds of the invention may also be used in the formation of a LCP layer by casting a LCP compound according to the first aspect of the invention or a mixture according to the third aspect of the invention onto a substrate. A fourth aspect of the invention therefore provides a method forming a LCP network comprising forming a LCP layer including a compound of formula (I) and cross-linking the layer. Liquid crystalline mixtures according to the third aspect of the invention may also be used in the manufacture of LCP networks in a similar way.
The invention also includes, in a fifth aspect of the invention, a cross-linked LCP network comprising a compound of formula (I) in a cross-linked form. Cross-linked LCP networks comprising a mixture according to the third aspect of the invention in cross-linked form may also be included in this aspect of the invention.
A sixth aspect of the invention provides the use of a compound of formula (I) in the preparation of an optical or an electro-optical device. The use, in the preparation of an optical or electro-optical device, of liquid crystalline mixtures according to the third aspect of the invention is also included in this aspect of the invention.
A seventh aspect of the invention provides an optical or an electro-optical device comprising a compound of formula (I) in a cross-linked state. An optical or electro-optical device comprising a LCP liquid crystalline mixture in a cross-linked state according to the third aspect of the invention is also included in this aspect of the invention.